(a) Field of the Invention
The present invention relates to a method for forming metal wirings of a semiconductor device.
(b) Discussion of the Related Art
Typically, in a semiconductor metal wirings are formed from conductive materials for electrically connecting the semiconductor devices and pads on a semiconductor substrate. Examples of conductive materials include aluminum, aluminum alloy, copper, and the like.
In order to connect the electrodes and pads isolated by dielectric layers of oxide, contact holes are formed by selectively etching the dielectric layers, and metal plugs are filled inside the holes. The metal wirings are formed by depositing and patterning a metal thin layer.
The metal plugs are formed from tungsten or copper, and a titanium nitride (Tin) layer is formed on inner walls of the contact hole to prevent diffusion of the tungsten or the copper through a CVD process.
However, the TiN layer formed in such manner contains impurities, such as C and N, which displace the TiN layer. Thus, the impurities reduce the protection against diffusion as well as cause high resistance.
In order to solve this problem, a known plasma process uses N2 and H2 gases to reduce the resistance of the TiN layer and to increase concentrations of the TiN layer, thereby increasing the protection against diffusion.
However, the known plasma process does not work well on the sidewalls of the contact holes, and thus current leakages occur between the contact holes.